Process and apparatus for vulcanization



Aug. 26, 1947.

C. M. CANFIELD PROCESS AND APPARATUS FOR VULCANIZATION Filed 001:. 20, 1944 iNVENTOR ATTORNEY Patented Aug. 26, 1947 PROCESS AND APPARATUS FOR VULCANIZATION Charles M. Canfield, Utica, N. Y., assignor to General Cable Corporation, New York, N. Y., a corporation of New Jersey Application October 20, 1944, Serial No. 559,585

6 Claims.

This invention relates to the continuous vulcanization of insulated electrical conductors.

In processes and apparatus which have been developed for the continuous vulcanization of insulated electrical conductors, it is customary to run the metallic conductor at high speed (frequently 700 or more per minute) successively through (l) an extrusion head where the insulating compound is applied to the moving conductor, (2) a vulcanizing chamber where the insulated conductor is subjected to heat and pressure, usually by application of steam at pressures above 200 lbs. per square inch, and (3) a cooling trough or tube where the vulcanized insulated conductor is cooled before being reeled. Other accessory devices may be included in the complete apparatus, such as a preheater, a dryer and a soapstone duster, but the essential components are as stated above.

In the use of such processes and apparatus much difficulty has been experienced due to socalled blistering of the insulating compound. The difiiculty has been caused, apparently, by entrained air and moisture which may be entrapped within the insulating jacket as the jacket is applied during the extrusion process and prior to vulcanization, and is particularly acute in cases where the conductor is stranded and where the conductor is covered with a cotton jacket prior to applying the insulating compound. The seriousness of the difiiculty is also increased when using insulating compounds containing synthetic rubber of the Buna S type.

It is an object of the present invention to provide methods and apparatus for overcoming this difiiculty and providing a product in which the insulation is applied more tightly and is of increased density and uniformity.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which,

Figure 1 is a side elevation of the apparatus.

Figure 2 is an enlarged sectional view of the exit end of the cooling chamber.

Figure 3 is an enlarged sectional view of the exit end of the 'vulcanizin'g chamber and the entrance end of the cooling chamber.

In all of the prior art apparatus with which I am familiar, it is customary to cool the vulcanized insulated conductor at atmospheric pressure. Usually the conductor emerges from the vulcanizing chamber through a seal into the atmosphere, then passes-arounda pulley, then is led into a cooling trough or tube containing cooling water at atmospheric pressure. According to the present invention, I lead the vulcanized insulated conductor from the vulcanizing chamber through a seal directly into a cooling chamber containing cooling water at elevated pressure. The pressure maintained on the cooling water should preferably be less than the steam pressure in the vulcanizing chamber, butshould be sufiiciently high to exceed the internal pressures developed by the air or moisture within the insulation during the vulcanization process. Such pressure should be maintained until the temperature of the insulated conductor has been reduced by the cooling water sufficiently to reduce the internal pressures substantially to atmospheric pressure. For example, in the case where the pressure in the vulcanizing chamber is maintained at 225 to 250 lbs. per square inch and the conductor is travelling at a rate of 700 per minute, a pressure of to lbs. per square inch maintained while the conductor is travelling through a cooling chamber 25 to 30' long has been found to give satisfactory results, using cooling water at ordinary hydrant temperatures.

A suitable arrangement of apparatus for practicing the invention is shown in the drawings, in which the exit end of the vulcanizing chamber I is provided with a diaphragm seal 2 having an aperture 3 therethrough for passage of the insulated conductor 4. The diaphragm is held in sealing engagement with the conductor by means of a sleeve 5 actuated by a lever 6 connected by rod 7 to a pneumatic piston device designated generally by 8, by means of which the pressure on the diaphragm may be kept constant, or ad- J'usted as desired.

The cooling chamber comprises an elongated pipe or tube 9 coupled directly toa tube H] extending to the lever housing H and providing an open passageway so that the hydraulic pressure maintained in the cooling chamber may extend through tube l0 and sleeve 5 to the diaphragm 2 so that the steam pressure on one side of the diaphragm is opposed by the hydraulic pressure of the other. Thus, as soon as the conductor leaves the vulcanizing chamber through the diaphragm, it is immediately subjected to hydraulic pressure and to the cooling effect of the cooling water,

This hydraulic pressure is maintained throughout the entire length of th cooling chamber, the exit "end of the cooling chamber being provided with a diaphragm seal l2 mounted'in a housing [3 and held in sealing engagement with the conductor bya sleeve l 4 operated by a pneumatic piston 15in the manner previously described. Suitable inlet and outlet connections l6, l! are provided :for circulating cooling water through the cooling chamber, the inlet fcon'nection allB entering the cooling chamber through housing I l. The pressure and flow of water may be maintained and controlled in any suitable manner.

It is not necessary that the conductor be reduced to room temperature during its passage through the cooling chamber, so long as its temperature is reduced sufiiciently to reduce the internal pressures substantially to atmospheric pressure. If desired, after emerging from the cooling chamber, the conductor may be cooled additionally either by water or by air before drying, dusting and reeling.

I am aware that in the past it has been proposed to utilize what is known as water seals at the ends of the vulcanizing chamber in which water under pressure is utilized as a means of sealing the vul canizing chamber. Such water seals are relatively short, however, and at the customary rates of travel of the insulated conductor therethrough, the cooling effect is entirely insufficient to reduce the internal pressures sufilciently to prevent blistering of the insulation when the conductor emerges from the seal and the water pressure is relieved. Blistering is, in fact, a serious problem in machines equipped with such Water seals.

It will be understood that the invention may be variously modified and embodied within the scope of the subjoined claims.

I claim as my invention:

1. Process for the continuous vulcanization of insulated electrical conductors which comprises passing a conductor continuously through a vulcanizing zone, subjecting said conductor to heat and pressure while passing through said vulcanizing zone, thereby vulcanizing the conductor and at the same time developing undesirable high internal pressures in entrapped pockets of air and moisture, passing said conductor continuously and directly from said vulcanizing zone to a cooling zone, and continuously maintaining a uniform pressure on said conductor while it is passing through said cooling zone, the pressure in the cooling zone being in excess of the internal pressures developed in said conductor while passing through said vulcanizing zone and being maintained until the internal pressures have been re duced by the cooling of the conductor to values such that there is no danger of blistering when the conductor emerges from the cooling zone to atmospheric pressure.

2. Process for the continuous vulcanization of insulated electrical conductors which comprises passing a conductor continuously through a vulcanizing zone, subjecting said conductor to steam at a pressure in excess of 200 lbs. per square inch while passing through said vulcanizing zone, thereby vulcanizing the conductor and at the same time developing undesirable high internal pressures in entrapped pockets of air and moisture, passing said conductor continuously and directly from said vulcanizing zone to a coolin zone, and continuously subjecting said conductor to cooling water at a pressure in excess of 150 lbs. per square inch, but less than the vulcanizing pressure, while passing through said cooling zone, said water pressure being uniform throughout the said cooling zone and being maintained until the internal pressures developed in said conductor while passing through said vulcanizing zone have been reduced by the cooling of the conductor to values such that there is no danger of blistering when th conductor emerges from the cooling zone to atmospheric pressure.

3. In apparatus for the continuous vulcanization of insulated electrical conductors wherein an 4 insulated conductor passes continuously through an elongated vulcanizing chamber containing steam under high pressure and emerges directly through an exit seal in the chamber wall to the atmosphere with danger of blistering the insulation upon the abrupt drop in pressure on the hot conductor, the combination with the vulcanizing chamber of an elongated cooling chamber forming an extension of the vulcanizing chamber beyond the said exit seal, a second exit seal in the distant end of the cooling chamber permitting continuous passage of the moving conductor therefrom to the atmosphere, and means for circulating cooling fluid through said cooling chamber under pressure approaching the pressure in the vulcanizing chamber, the cooling chamber providing an open, unimpeded passage-way for the cooling fluid along the moving conductor so that the high pressure is maintained uniformly throughout its entire length between the two said seals.

4. In apparatus for the continuous vulcanization of insulated electrical conductors traveling through a vulcanizing chamber maintained at 225 to 250 pounds per square inch steam pressure and through a cooling chamber maintained at 150 to 175 pounds per square inch water pressure j at ordinary hydrant temperatures the combination set forth in the preceding claim characterized by the fact that the cooling chamber is of the order of 25 to 30 feet in length.

5. In apparatus for the continuous vulcanization of insulated electrical conductors which includes a vulcanization chamber, means for applying steam at high pressures to a conductor passing through said chamber, and entrance and exit seals permitting the conductor to enter and leave the said chamber continuously while maintaining high steam pressure therein, the combination with the vulcanization chamber of an elongate tube connected at one end directly to the said chamber and forming an extension thereof beyond the exit seal, a third seal at the other end of the extension tube permitting the conductor to leave the tube continuously, and means for circulating a cooling fluid under high pressure through the extension tube, the tube providing an open, unimpeded passage-way for the cooling fluid along the moving conductor so that the high pressure is maintained throughout the entire length of the cooling tube.

6. In apparatus for the continuous vulcanization of insulated electrical conductors traveling through a vulcanizing chamber maintained at 225 to 250 pounds per square inch steam pressure and through a cooling chamber maintained at to 1'75 pounds per square inch Water pressure at ordinary'hydrant temperatures the combination set forth in the preceding claim characterized by the fact that the cooling chamber is at least 25 feet in length.

CHARLES M. CANFIELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

